java基础语法
Demo03
public class Demo03 {
public static void main(String[] args) {
int i = 10;
int j = 010;
int k = 0x10;
System.out.printf("%d %d %d",i,j,k); //10 8 16
System.out.println();
float f = 0.1f; //离散 有限 大约 接近但不等于 最好避免使用浮点型进行比较
double b = 0.1;
System.out.println(f == b); //false
float f1 = 321543513f;
float f2 = f1 + 1;
System.out.println(f1 == f2); //true
char r = (char)20013;
System.out.println(r); //中
}
}
Demo06
位运算
/**
* @version 1.0.0
* @time 2022/7/1 15:43
* @Author SmallWatermelon
*/
public class Demo06 {
public static void main(String[] args) {
/*
* 位运算：
* A = 0011 1100
* B = 0000 1101
*
* A&B = 0000 1100
* A|b = 0011 1101
* A^B = 0011 0001
* ~B = 1111 0010
*
* 2*8 = 16 2*2*2*2
* 2 << 3 (效率极高,与底层接触)
*
* 0000 0001 1
* 0000 0010 2
* 0000 0011 3
* 0000 0100 4
* 0000 1000 8
* 0001 0000 16
* */
System.out.println(2 << 3);
}
}
Demo07
字符串连接符
/**
* @version 1.0.0
* @time 2022/7/1 16:07
* @Author SmallWatermelon
*/
public class Demo07 {
public static void main(String[] args) {
int a = 10;
int b = 20;
System.out.println("" + a + b); //1020
System.out.println(a + b + ""); //30
}
}
包机制 & JavaDoc
包机制
包应该生成为: com.baidu.www
package com.swm.base;
/**
* @time 2022/7/1 16:20
* @Author SmallWatermelon
* @since 1.8
*/
public class Doc {
String name;
/**
*
* @param name
* @return
* @throws Exception
*/
// 两个斜杠加*即可生成上面注释
public String test(String name) throws Exception{
return name;
}
}
##
JavaDoc 生成方法
进入文件夹内输入cmd 以下命令
javadoc -encoding UTF-8 -charset UTF-8 需要生成的类
递归
package com.swm.method;
/**
* @version 1.0
* @time 2022/7/2 10:45
* @Author SmallWatermelon
* @since 1.8
*/
//递归
//数据较小的时候使用
public class Demo06 {
public static void main(String[] args) {
Demo06 demo06 = new Demo06();
int f = demo06.f(5); //f = 120
System.out.println("f = " + f);
}
public static int f(int i) {
if(i == 1) {
return 1 ;
}else {
return i * f(i - 1);
}
}
}
多维数组
package com.swm.array;
/**
* @version 1.0
* @time 2022/7/3 13:50
* @Author SmallWatermelon
* @since 1.8
*/
public class Demo08 {
public static void main(String[] args) {
int[][] ints = new int[11][11];
ints[1][2] = 1;
ints[2][3] = 2;
for (int[] i:ints
) {
for (int k:i
) {
System.out.print(k + "\t");
}
System.out.println();
}
System.out.println("=============");
int sum = 0;
for (int i = 0; i < 11; i++) {
for (int j = 0; j < 11; j++) {
if (ints[i][j] != 0)
sum++;
}
}
System.out.println("sum = " + sum);
//稀疏数组
int[][] ints1 = new int[sum + 1][3];
ints1[0][0] = 11;
ints1[0][1] = 11;
ints1[0][2] = sum;
int count = 0;
for (int i = 0; i < ints.length; i++) {
for (int j = 0; j < ints[i].length; j++) {
if (ints[i][j] != 0) {
count++;
ints1[count][0] = i;
ints1[count][1] = j;
ints1[count][2] = ints[i][j];
}
}
}
for (int[]